Discussion Forum - Northstar Chevelle Club

SShink · 3K+ Club

Mystery rocker arm and noise...

bowtie · Secretary

no idea on the rockers

I would check the basics like carb settings, timing, etc just to make sure you're square there. Does the pop happen only at idle, on the gas, coming off the gas, etc? Are there sign or sounds of a gasket leak? air coming in would also be air coming out as there's pressure from engine out the pipe, so there should be a tick or sign of leak in exhaust, that's why I'm thinking a tuning issue.

SShink · 3K+ Club

bowtie wrote:

no idea on the rockers

I would check the basics like carb settings, timing, etc just to make sure you're square there. Does the pop happen only at idle, on the gas, coming off the gas, etc? Are there sign or sounds of a gasket leak? air coming in would also be air coming out as there's pressure from engine out the pipe, so there should be a tick or sign of leak in exhaust, that's why I'm thinking a tuning issue.

I've checked the timing (good), installed new plugs and wires, and it could be the carb as it's 10+ years old and who knows the last time it was rebuilt. Although, I swapped a Holley on that Kevin had, and the sound didn't change at all so I'm ruling out the carb.

It pops real loud on the first cold startup and then goes to an intermittant muffled pop at idle. Increasing the rpm increases the frequency of the sound. It does sound like an exhaust leak that is contained inside the headers if that makes any sense.

Kevin and I were also thinking that one of the exhaust valves is not closing completely which is why I pulled the valve cover and looked at the rocker arms and springs. Nothing looked amiss.

Chris R · 2K+ Club

Looks like they are Crane Cams Energizer rockers.

http://www.summitracing.com/parts/CRN-13744-1/?rtype=10

The first thing I would do is Loosen all 16 rockers and re adjust them. You can start with placing the engine and at #1 TDC and go from there. Then you know your valves are adjusted.

A popping noise isnt normal but roller rockers a more rattley then stamped rockers. I have Harlan Sharp rockers on my 66 and it did take some getting used to compared to the quiet stamped rockers. I originally thought something was wrong but I searched and asked professional engine builders and found out that was normal. I cant remember if that was just with the Harlan Sharps though, I dont have expierence with anything else really. I know they never came loose or gave me any problems after something like 7K plus miles in the first 5 years I had them on before I stopped driving the car.

It also couldnt hurt to check those pushrods to make sure they are in good shape. Dont want to have another problem like Craig had.

SShink · 3K+ Club

Chris R wrote:

Looks like they are Crane Cams Energizer rockers.

http://www.summitracing.com/parts/CRN-13744-1/?rtype=10

The first thing I would do is Loosen all 16 rockers and re adjust them. You can start with placing the engine and at #1 TDC and go from there. Then you know your valves are adjusted.

A popping noise isnt normal but roller rockers a more rattley then stamped rockers. I have Harlan Sharp rockers on my 66 and it did take some getting used to compared to the quiet stamped rockers. I originally thought something was wrong but I searched and asked professional engine builders and found out that was normal. I cant remember if that was just with the Harlan Sharps though, I dont have expierence with anything else really. I know they never came loose or gave me any problems after something like 7K plus miles in the first 5 years I had them on before I stopped driving the car.

It also couldnt hurt to check those pushrods to make sure they are in good shape. Dont want to have another problem like Craig had.

Chris I think you are the winner on ID'ng the rockers! That looks exactly like what's in there. Good to know whoever built the motor used good parts. They do make more noise than I would expect from a roller, but that explains it.

John D also thinks it might be a valve setting issue that is causing the popping sound. I will go through the valves and relash them to give it a try.

Question-When you adjust valves do you warm up the engine first to pump up the lifters or do you set them when cold?

67ss · 1K+ Club

You might also have a valve sticking in the guide. I have seen that on more than a few big blocks. But I agree trying to adjust the valves first is a good start. If that does not do it pull plug wires off one at a time until the noise stops and then you will know which cylinder(s) it is.

SShink · 3K+ Club

I checked the valve train and it's fine. I did discover that by removing the # 1 plug wire the sound stopped. I then put a new header gasket on and it had a loud puffing sound out of # 1 exhaust. I then double gasketed the header (it had 2 gaskets when I started which indicates to me that there's been an issue in the past) and it quieted the header leak but the original sound was still there.

I did notice a lot of carbon under the # 1 header tube which I think was from the past gaskets, but it might still be leaking there. I recorded it and you can see the carbon on the block and hear the popping sound through the exhaust at the back of the car.

http://www.youtube.com/watch?v=vICKkwBBQkI

So, I think it is either pull the header (which means pulling the motor) and having the flange ground flat or putting in cast iron exhaust manifolds which I was going to do to make the motor look more stock. I don't mind giving up a few horsepower if it solves all the header problems (hot starters, burnt plug wires, exhaust leaks, etc.).

Just have to decide which path to take. It's always something... but that's part of why I like the hobby (at least that's what I tell myself!). biggrin

frank · Active Member

stan met you a few times been watching you on here a wonder why you just don't build a car. buy a decent car which it looks like you have done then have somebody build you a motor of your dreams. get a good tranny that fits your game and a rearend to match and you are done. i have al cheetah build mine like everybody else i know does, we beat them to hell and never a problem.

SShink · 3K+ Club

frank wrote:

stan met you a few times been watching you on here a wonder why you just don't build a car. buy a decent car which it looks like you have done then have somebody build you a motor of your dreams. get a good tranny that fits your game and a rearend to match and you are done. i have al cheetah build mine like everybody else i know does, we beat them to hell and never a problem.

Frank, good to see you on the forum again. I try to buy Chevelle's that don't need any bodywork and if it needs mechanical work I can tackle that. This Chevelle has a ton of options and the body work is very good considering it was done 10+ years ago.

So, I knew going into it that I might have to do some motor and trans work since it has a built TH400 and deep gears. I will probably end up pulling the motor/trans to detail the motor (needs new flex plate for sure as the ring gear is chewed up from a previously non-shimmed starter) and change the trans to a 4 speed auto.

The 402 sounds solid other than the exhaust leak and if all it takes is some exhaust work I can deal with that.

Nobody probably believes me... but if I get this one set up the way I like them (good cruiser with decent highway manners and plenty of power) I think this is the one I'm going to hang onto since I really like the way it looks and all the options it has. smile

Derek69SS · Founding Member

SShink wrote:
Nobody probably believes me... but if I get this one set up the way I like them (good cruiser with decent highway manners and plenty of power) I think this is the one I'm going to hang onto since I really like the way it looks and all the options it has.

Nope, I'm not buying it... evileye

biggrin

Good luck Stan... some days I really envy how you get a "new" car every couple years. I get too attached to mine, and keep them forever. I always want another car, but don't sell any, or have room to keep them all.